92 ZOOLOGY. 
mantle closed beneath according to most authors, but above according to 
Rang. Most of them have three hearts. The mouth is armed with strong 
mandibles much like those of a parrot, adapted for crushing the shells of 
erustacea and mollusea, and the tongue is armed with pointed horny teeth. 
The eyes are either pedunculated or level with the surface, and they have 
the sense of vision fully developed. They have also an organ of hearing. 
The arms are usually cotyligerous, or studded with suckers like cupping 
glasses, which enable them to hold fish and other living prey. The Greeks, 
in naming these sucking cups, made use of the word Aotylus (in composition), 
whence the English name cuttle-fish is derived. The cotyls are sometimes 
armed within with curved hooks, which assist in holding and destroying 
the prey. Onychoteuthis has a pair of arms much longer than the rest, the 
terminal expansion of which is studded with rows of hooks, but the power 
is increased by a simple sucker on each wrist (as it may be called), which 
are applied together to keep the extremities of the arms in contact. 
There is a fleshy infundibulum or funnel opening before the neck, and 
serving as an outlet for the feeces and water from the branchie. The water 
ejected from the branchial sac through the funnel is a principal agent in 
locomotion, by means of which the animal can move backwards with great 
swiftness. Inspiration and expiration are regular in these animals. “The 
first is effected,” says Dr. Coldstream, “by a gradual dilatation of the sac in 
every direction, but particularly at the sides, accompanied by a subsidence — 
of the lateral valves, collapse of the walls of the funnel, and a rush of water 
through the lateral openings into the sac. Inspiration being completed, the 
lateral valves are closed, the sac is gradually contracted, the funnel erected 
and dilated, and the water expelled through it with great force in a con- 
tinuous stream.” An Octopus with a sac four inches long was found to 
respire ten times in a minute. 
The Cephalopoda are either naked, or provided with an external shell. 
Some of the former are brilliantly colored, red, purple, or bluish, and they 
are remarkable for the rapidity and extent to which the colors change. In 
habits they are rapacious and active, moving continually, and some of them 
shoot through the water like an arrow. 
Agassiz thinks that in this order the Nautilids are the lowest, and Sepiadee 
the highest. We will here follow the classification of D’Orbigny, according 
to which the class is divided into two orders, Acetabulifera and Tentaculi- 
fera, the former being subdivided into two tribes, Octopoda and Decapoda,* 
containing seven families conjointly. As the name implies, the Acetabulifera 
are provided with cotyls, and the head is distinct, characters which do not 
exist in the Tentaculifera; and the former have two, and the latter four 
branchiee, whence Owen’s naines of Dibranchiata and Tetrabranchiata. 
. Tribe Octocera. 
Fam.1. Octopide. The genus Octopus (O. octopodius, Linn. (Sepia) pl. 
76, fig. 75) is the polypus of the ancients, whence the French name poulpe 
* A name pre-occupied among the Crustacea, and on this account we employ the terms 
Octocera and Decacera, usually attributed to ao 
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